State+Actions

components.counter\.js

import Component from "@glimmer/component";
import { tracked } from "@glimmer/tracking";
import { action } from "@ember/object";

export default class CounterComponent extends Component {
  @tracked count = 0;

  get total() {
    return this.count * this.args.multiple;
  }

  @action
  change(amount) {
    this.count = this.count + amount;
  }

  @action
  double() {
    this.args.updateMultiple(this.args.multiple * 2);
  }
}

components.double-it\.js

import Component from "@glimmer/component";
import { tracked } from "@glimmer/tracking";
import { action } from "@ember/object";

export default class DoubleItComponent extends Component {
  @tracked multiple = 1;

  @action
  updateMultiple(newMultiple) {
    this.multiple = newMultiple;
  }
}

controllers.application\.js

import Controller from '@ember/controller';

export default class ApplicationController extends Controller {
}

templates.application\.hbs

<DoubleIt/>

templates.components.counter\.hbs

<p>{{this.count}}</p>
<p>× {{@multiple}}</p>
<p>= {{this.total}}</p>

<button {{on "click" (fn this.change 1)}}>+1</button>
<button {{on "click" (fn this.change -1)}}>-1</button>

<button {{on "click" this.double}}>Double It</button>

templates.components.double-it\.hbs

<Counter @multiple={{this.multiple}} @updateMultiple={{this.updateMultiple}} />

tests.test-helper\.js

import Application from '../app';
import config from '../config/environment';
import { setApplication } from '@ember/test-helpers';
import { assign } from '@ember/polyfills';
import { start } from 'ember-qunit';

let attributes = {
  rootElement: '#test-root',
  autoboot: false
};
attributes = assign(attributes, config.APP);

let application = Application.create(attributes);
setApplication(application);

start();

twiddle\.json

{
  "version": "0.17.0",
  "EmberENV": {
    "FEATURES": {},
    "_TEMPLATE_ONLY_GLIMMER_COMPONENTS": false,
    "_APPLICATION_TEMPLATE_WRAPPER": true,
    "_JQUERY_INTEGRATION": true
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.17.0",
    "ember-template-compiler": "3.17.0",
    "ember-testing": "3.17.0"
  },
  "addons": {
    "@glimmer/component": "1.0.0"
  }
}